alpha, alpha&#39;-(1, 4-piperazinediyl) bis (3, 5-dialkyl-4-hydroxythiobenzaldehyde) compounds



. 3,186,993 a,u'-(1,4-PIPERAZINEDIYL)BIS(3,5-DIALKYL-4-HY- DROXYTHIOBENZALDEHYDE) COMPOUNDS Gordon G. Knapp,.Royal Oak, Micin, assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed June 7, 1962, Ser. No. 200,625

9 Claims. (Cl. 260268) This invention relates to a novel class of compounds, their preparation and their use as antioxidants. More particularly, it relates to a novel and unusual class of 11,11. (1,4 piperazinediyl)bis(3,5 dialkyl 4 hydroxythiobenzaldehyde) compounds, the methods for their preparation and the employment of these novel compounds as stabilizers and antioxidants for organic material.

In the past, benzyl amines have been suggested for use as antioxidants for various organic media. Their acceptance has been limited due to many and variable factors such as volatility, compatibility, solubility and others. Sulfur-containing compounds have also been suggested for use as antioxidants and their acceptance has also been hampered by compatibility factors. Further, in those areas where benzyl amines were found effective, sulfurcontaining compounds were found to be ineffective or actually detrimental. Likewise, in those areas where sulfur-compounds have been found to compounds have found noutility. Clearly then a need exists for an effective antioxidant for use in both those areas in which benzyl amines have been found to be suitable and in which sulfur-containing compounds have been found to be suitable. Further, the antioxidant must be of a large enough molecular weight to be soluble and substantially non-volatile and also be easily prepared at low cost.

Accordingly, an object of this invention is to provide novel and useful chemical compounds. Another object is to provide novel and useful sulfur-containing benzyl amine type compounds which are easy to prepare, low in cost, have a high degree of solubility and have low volatility. A further object is to provide novel and useful cz,u.'-( 1 ,4-piperazinediyl bis 3,5 -dialkyl-4-hydroxythiobenzaldehyde) compounds. Still another object is to provide processes for preparing the novel piperazine thiobenzaldehyde of this invention. A still further object is to provide improved compositions of matter containing the various compounds of this invention. A specific object is to provide lubricating oil stabilized against oxidative deterioration. Other important objects of this invention will be apparent from the following description.

The above and other objects are accomplished by provision of a compound having the formula:

-n-propyl-S-p-n-tridecylbenzylthiobenzaldehyde); ct,a'-( 1 ,4-

piperazinediyl)bis(3,5 di tert butyl 4 hydroxythiobenzaldehyde); 11,02 (1,4 piperazinediyl)bis(3,5 di nocty1-4-hydroxythiobenzaldehyde); a,oL'-( 1,4 piperazinediyl)bis[3,5-di-(u,amethylbenzyl)-4 hydroxythiobenzaldehyde']; 01,11 (1,4 piperazinediyl)bis(3 benzyl- S-secbe effective, amine ice butyl-4-hydroxythiobenzaldehyde); a,a' (1,4-piperazinediyl)bis(3,5-di-n-eicosyl 4 hydroxythiobenzaldehyde); a,a-(1,4-piperazinediyl)bis(3,5dimethyl-4 hydroxythiobenzaldehyde); and a,a' -(1,4-piperazinediyl)bis(3,5-di-amethylb enzyl-4-hydroxythiobenzaldehyde) The compounds of this invention are water insoluble and non-polar. They range from white to yellow crystalline solids to viscous amber liquids. They are ashless and non-volatile facilitating their incorporation into a wide range of organic material.

A preferred embodiment of this invention consists of compounds of the above formula wherein R is an alkyl group having from 1-12 carbon atoms and R is an alphabranched alkyl group having from 3-12 carbon atoms.

These compounds are more effective antioxidants than other compounds within the scope of this invention. Among the compounds represented by this embodiment arei a,u'-(1,4-piperazinediyl)bis(3,5 di tert-butyl-4-hydroxythiobenzaldehyde) a,a-(1,4-piperazinediyl)bis[3-n butyl-4-hydroxy-5-( l-methyl-n-pentyl) thiobenzaldehyde] a,a'-(l,4-piperazinediyl)bis(4 hydroxy 3,5-diisopropylthiobenzaldehyde); ot,m"- (1,4 piperazinediyl)bis(3-tertbutyl-4-hydroxy 5 methylthiobenzaldehyde); a,a'-(1,4- piperazinediyl)bis(4-hydroxy-3,S-di n pentylthiobenzaldehyde); and a,a'-(1,4-piperazinediyl)bis('3-tert-butyl-5- ethyl-4-hydroxythiobenzaldehyde) The most particularly preferred compound of this invention is a,a-(1,4-piperazinediyl)bis(3,5-di-tert-butyl-4- hydroxythiobenzaldehyde).' This compound is most particularly preferred because it has excellent antioxidant activity in lubricating oils and other organic media, to a greater extent than the other compounds of this invention.

The novel compounds of this invention can be prepared by two methods. In one embodiment of this invention the compounds are prepared by reacting a benzylpipera- Thus, ,a'-(1,4-piperazinediyl)bis(3,5- di-tert-butyl-4-hydroxythiobenzaldehyde) -is readily prezine with sulfur.

pared by reacting a,a'-(1,4-piperazinediyl)bis(2,6-di-tert butyl-pcresol) with sulfur.

The above reaction can be illustrated by the following general equation:

wherein R and R are as in Formula I. v i

The preparation of the a,ix'-(l,4-piperazinediyl)bis (2,6-dialkyl-p-resol) compounds is described in application Serial No. 200,624, filed June 7, 1962, and with the present application entitled Piperazine Derivatives, the inventor being Harold D. Orlotf. They can be prepared by reacting a 2,6-dialkylphenol and piperazine and formaldehyde. Thus, u,a-(1,4-piperazinediyl)bis(2,6-di-tertbutyl-p-cresol) can be prepared by reacting 2,6-di-tertbutylphenol with piperazine and formaldehyde.

' The temperatures employed in the reaction of Equation 11 vary from about C. to the reflux temperature of the reaction mixture, but no higher than about 300 C., at reaction times of from a few minutes to one week or more to give a good yield of product.

The preferred temperature range is from about C. to about 220 C. At this temperature range the reaction proceeds smoothly, at a sufficiently rapid rate to give it messes 3 good yield of product in a reasonable time with a minimum of undesirable side reactions.

In another embodiment of this invention the compounds are prepared by reacting a 3,5-dialkyl-4-hydroxybenzaldehyde, sulfur and piperazine. diyl)bis(3,5 di-tert-butyl-l-hydroxythiobenzaldehyde) is readily prepared by reacting 3,S-di-tert-btuyl-4-hydroxybenzaldehyde with sulfur andpiperazine.

wherein R and R, are as in FormulaI.

The preparation of the 3,5-dialkyl-4-hydroxybenzaldehyde is described in pending application S.N. 77,276 entitled Stabilized Plastic, filed December 21, 1960, the inventors being Gordon G. Knapp and Calvin J. Worrel. They can be prepared by the bromination of the corresponding 2,6-dialkyl-p-cresol in the presence of alcohol with a subsequent hydrolysis of the brominated cresol. Thus, 3,S-di-tert-butyl-4-hydroxybenzaldehyde can be prepared by brominating 2,S-di-tert-butyl-p-cresol and subsequently hydrolyzing the brominated cresol.

The temperatures employed in practicing this embodiment vary from about 50 C. to the reflux temperature of the highest boiling reaction mixture, or about 300 C., at reaction times of from a few minutes to one week or more to give a good yield of .product.

A- preferred temperature range is from about 80 C. to 135 C. At this temperature range the reaction proceeds rapidly giving a high yield of product with a minimum of undesirable side reactions.

In both the above reactions, in order to insure complete utilization of the starting phenolic compound it is desirable to use an excess of sulfur. Furthermore, in order for the reaction to proceed more etficiently elevated pressure may be employed.

Both'reactions maybe conducted with or without the aid of a solvent. For most of the compounds it is preferred not to use a solvent due to the lack of solubility of free sulfur. However, for certain compounds a solvent may be desired where the phenolic compound is a high ,melting solid and not liquid at the reaction temperature. Such solvents are the higher boiling glycol ethers and alcohols such as ethylene glycol-mono-n-butyl ether, ethylene glycol-monophenyl ether, ethylene glycol-monobenzyl ether, n-hexyl alcohol, cyclohexanol, n-octyl alcohol, capryl alcohol, n-decyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, benzyl alcohol, n-heptyl alcohol, nnonyl alcohol, n-undecyl alcohol and n-dodecyl alcohol. When lower temperatures are desired other solvents may be used such as dioxane or pyridine.

In conducting the reaction of Equation III a convenient solvent is the piperazine reactant itself. When using piperazine as a solventa convenient reaction temperature is the boiling point of piperazine, about 145 C. After the compounds have been formed they can be removed by any conventional means such as solvent extraction or filtration.

The molar ratio of sulfur to phenolic compounds in both the reactions of Equations II and III can be varied from about 1:1 to about 10:1 or more and still produce a good yield of compound; In general, it has been found that increasing the molar ratio of sulfur to phenolic compound beyond that of about 5:1 affords only slightly increased yields of compounds in relation to the amount of sulfur used. Thus, a preferred embodiment of this in- Thus, a,a-(l,4-piperazine- 1 This reaction can be illustrated by the following general equation:

vention is the preparation of a highly effective antioxidant material by the reaction of Equation II or III wherein the molar ratio of sulfur to phenolic compounds is from about 1:1 to about 5:1.

An excellent yield of compound is obtained with a minimum amount of unreacted phenolic compound when the molar ratio of sulfur to phenolic compound is about 2:1. Thus, a particularly preferred embodiment of this invention isthe preparation of a highly eifective antioxidant material by the reaction of Equations II or III where-- outlined in Equation II.-

Example 1 In a react-ion vessel equipped with a stirrer, temperature measuring means and heating means were placed 26.1 parts of a,a'-(1,4-piperazinediyl)bis(2,6-di-tert-butylp-cresol) and 5.6 parts of sulfur. The mixture was heated to 145 C.-1'55 C. for one hour and then allowed to cool to room temperature. The resultant material was then triturated' with benzene. The benzene was evaporated andthe residue was then triturated with nhexane and filtered to yield'an amorphous orange solid which was triturated with hot ethyl acetate to yield bright yellow a,a'-( 1,4-pipera'zinediyl) bis(3,'5-di--tert-bu'tyl-4-hydroxythiobenzaldehyde), with a melting point of 270 C. AnaIysis.-Calculated for c ,H N,o,s,: 11.0 percent sulfur, 4.81 percent nitrogen. Found: 11.2 percent sulfur, 5.46 percent nitrogen. I

Theethyl acetate triturate from the above reaction was concentrated andcooledto yield a small amount of yellow' crystalline 3,5-di-tert-butyl-4-hydroxybenzyl-piperazine as a by-product, with a melting point of 197-199 C. Analysis.-Calculated for C H ON S: 9.59 percent-sulfur, 8.38 percent nitrogen. Found: 9.46 percent sulfur, 8.61 percent nitrogen.

Example 2 In a reaction vessel equipped with a stirrer, temperature measuring means and heating means are placed 261 parts of a,a' -(1,4-piperazincdiyl)bis(2-tert butyl-6-methyl-p-cresol) and 32 parts of sulfur in 500 parts of nhexyl alcohol. The mixture is heated to C. and kept at that temperature with stirring for one week. During this time a solid precipitates which is then filtered. This material is recrystallized from a 50 percent mixture of isooctane and ethanol to give ,a-(1,4-piperazinediyl)bis(B-tert-butyI'S-methyl 4 hydroxythiobenzaldehyde).

Good results are also obtained when other benzylpiperazines are treated in the manner of the above example. For example, the reaction of e,a'-(1 ,4-piperazinediyl)bis(2,6-diethyl-p-cresol) with sulfur in ethylene glycol-mono-n-butyl ether yields u,u'-l,4-(piperazinediyl) bis(3,5 diethyl-4-hydroxythiobenzaldehyde). Likewise, a,oz'-(1,4 piperazinediyl)bis[2,6 di (01,0: dimethylbenzyl)-p-cresol] can be reacted with sulfur in n-decyl alcohol to produce a,a'-(1,4-piperazinediyl)bis [3,5-di- (a,a-dimethylbenzyl -4-hydroxythiobenzaldehyde] Example 3 In a reaction vessel equipped with heating means, a stirrer and temperature measuring means are placed 303 parts of m,a-(l,4-piperazinediyl)bis(2,6-di-tert-butyl-pthe mixture i triturated with n-hexane. A precipitate is formed which is filtered and recrystallized from a 50 percent mixture of isooctane and ethanol to yield u,a'- (1,4- piperazinediyl)bis(3,5-di-tert butyl 4 hydroxythiobenzaldehyde) Following the procedure in Example 3 good results are also obtained when a,a-(l,4-piperazinediyl)bis|2- tert-butyl-6-(l-ethyl-n-decyl)p-cresol'] is reacted with sulfur to produce a,u-( l,4-piperazinediyl)bisl3-tert-butyl-S-('l-ethyl-n-decyl)-4-hydroxythiobenzaldehyde]. Likewise, u,a'-(1,4-piperazinediyl)bis[2-n-butyl-6-(l-mcthyln-pentyl)-p-cresol] can be reacted with sulfur to form a,a'(l,4 piperazinediyl)bis[3 n butyl-5-(1-methyl-n-' pentyl)-4-hydroxythiobenzaldehyde1.

Example 4 In a pressure vessel equipped with venting means, heating means, a stirrer and temperature measuring means are placed 275 parts of a,a-(l,4-piperazinediyl)bis(2,6-diisopropyl-p-cresol) and 16 parts of sulfur in 400 parts of capryl alcohol. The pressure vessel is sealed, heated to 150 C. and maintained at that temperature for 2 hours.

To a reaction vessel equippedwith heating means, a

stirrer and temperature measuring means are added 351 7 parts of a,a'-(l,4-piperazinediyl)bis(2,6-di-tert-butyl-pcresol) and 160 parts of sulfur. The mixture is heated to 220 C. and kept at that temperature with stirring for /2 hour. The mixture is then cooled to room tempera.- ture and triturated with n-hexane. A precipitate is formed which is filtered and recrystallized from a 50 percent mixture of n-hexane and ethanol to yield u,a'-(l,4-piperazinediyl)bis(3,5-di-tert-butyl 4 hydroxythiobenzaldehyde).

Good results are also obtained when a,a-(l,4-piperazinediyl)bis(2-tert-butyl-G-methyl-p-cresol) is reacted with sulfur in the abovemanner to yield a,a'-(1,4-piperazinediyl)bis(3-tert-butyl-5-methyl 4 hydroxythiobenzaldehyde). Likewise, a,u'-(1,4-piperazinediyl)bis[2,6-di- (tx-methylbenzyl)-p-cresol] can be reacted with sulfur to produce m,a-(1,4-piperazinediyl)bis[3,5 di (oz-methylbenzyl) -4-hydroxythiobenzaldehyde1.

Example 6 In a pressure vessel equipped with venting means, heating means, a stirrer and temperature measuring means are added 662 parts of a.a'-(1,4-piperazinediyl)bisLZ-ndecyl-6-(1,1-dimethyl-n-tetradecyl)-p-crcsol] and 256 parts of sulfur. The pressure vessel is sealed and heated to a temperature of 300 C. for, 5 minutes. It is then allowed to cool to room temperature and vented.' Upon trituration with n-hexane a solid precipitates from the mixture. This solid is filtered and recrystallized from a 50 percent mixture of n-hexane and ethanol to yield Q a- (l,4-piperazinediyl)bis[3 n decyl 4 -hydroxy-S-(1,ldimethyl-n-tetradecyl thiobenzaldehyde].

Good results are also obtained when other benzylpiperazines are reacted in the above manner. Thus, at,m'-( 1,4 piperazinediyl)bis(2,6-di-n-octyl-p-cresol) can be reacted with sulfur to produce a,ot-(l,4-piperazinediyl) bis (3,5-di-n-octyl-4-hydroxythiobenzaldehyde). Likewise, a,u'-(1,4-piperazinediyl)bis(2,6-di-tert-butyl-p-cresol) can be reacted, with sulfur to produce cad-(1,4:

pipera zinediyl)bis(3,5 di tert butyl-4-hydroxythiobenzaldehyde) Example 7 In a reaction vessel equipped with heating means, a;

stirrer, temperature measuring means and a reflux condenser are placed 477 parts of a, m'-(l,4-piperazinediyl) bis(2 n propyI-G-p-n-tridecylbenzyl-p-cresol) and 320 I parts of sulfur. The reaction mixture is refluxed for 2 days, cooled to room temperature and triturated with nhexane. A solid precipitates which is filtered and recrystallized from a 50 percent mixture of isooctane and ethanol to yield a,u'-(l,4-piperazinediyl)bis(4-hydroxy-3-n-propyl-S-p-n-tridecylbenzylthiobenzaldehyde) Good results are also obtained when a,u'-(1,4-piperazinediyl)bis(2-tert-butyl-6-methyl-p-cresol) is reacted with sulfur in the above manner to produce a, z'-(1,4-piperazinediyl)bis'(3 tert butyl 4 hydroxy 5 methylthiobenzaldehyde) The following examples, in which all parts and percentages are by weight, illustrate the compounds of this invention and their preparation according to the method outlined in Equation III.

. Example 8 In a reaction vessel equipped with heating means, a stirrer and temperature measuring means are placed 10.0

parts of 3,S-di-tert-butyl-4-hyd roxybenzaldehyde, 3.4 parts of sulfur and 5.0 parts of piperazine. The mixture is refluxed for 3 hours. The reaction mixture is then allowed to cool, dissolved in chloroform, washed in sequence with water, dilute sodium bacarbonate, dilute hydrochloric acid and finally water, dried and evaporated at room temperature to yield m,u-(1,4-piperazinediyl)bis( 3,5-di-tert-butyl- 4- hydroxy thiobenzaldehyde) Example 9 In a reaction vessel equipped with heating means, a stirrer and temperature measuring means are placed 343 parts of 3,S-di-(u,ot-dimethylbenzyl)-4-hydroxybenzalde-' hyde, 104 parts of piperazine and 32 parts of sulfur in 1000 parts of dioxane. The mixture is heated to 50 C. and maintained at that temperature for one week. The solvent is removed under reduced pressure and the resulting residue is taken up in a 50 percent mixture of hot ethanol andisooctan'e, filtered and cooled to yield a,a'- (1,4 piperazinediyl)bis[3.5 di (11,0: dimethylbenzyl)- 4-hyclroxythiobenzaldehydel.

Good results are also obtained when other benzaldehydes are reacted with piperazine and sulfur in a similar manner. Thus, 3.,S-diisopropyl-4-hydroxybenzaldehyde can be reacted with piperazine and sulfur in lauryl alcohol to produce u,a'-(l,4-piperazinediyl)bis(3,5-diisopropyl-4- hyd roxythiobenzaldehyde) droxybenzaldehyde can be reacted with piperazine and sulfur in benZyl alcohol to produce a,u-(1,4-piperazinediyl)bis(3,5 diethyl-4-hydroxythiobenzaldehyde). Also, 3-ethyl-5-tert-butyl-4-hydroxybenzaldehyde can be reacted with piperazine and sulfur in cetyl alcohol to produce a,a'- (1,4 piperazinediyl)bis(3.- ethyl-5-tert-butyl-4-hydroxythiobenzaldehyde).

Example 10- from a 50 percent mixture of n-hexane and ethanol to n eicosyl-' yield 11,11 (1,4 piperazinediyl)bis(3,5 di 4-hyd roxythiobenzaldehyde) Further, good rcsults are obtained when 3,5-di-sec-butyl- 4-hydroxybenzaldehyde is reacted with piperazine and Likewise, 3,5-diethyl-4-hy- I r 7 sulfur in stearyl alcohol to yield a, x'-(1,4-piperazinediyl) bis(3,5-di-sec-butyl-4-hydroxythiobenzaldehyde)'. Likewise, 3-n-butyl-4-hydroxy-5-(l-methyl-n-pentyl)benzaldehyde can be reacted with piperazine and sulfur in ethylene glycol-monobenzyl ether to yield a,ot'-(1,4-piperazinediyl) bis[3 n butyl 4 hydroxy'-5-(l-methyl-n-pentyl)-thiobenzaldehyde] Example 11 In a pressure vessel equipped with venting means, heating means, a stirrer and temperature measuring means are placed. 482 parts of 3,5-di-n-dodecyl-4-hydroxybenzaldehyde, 87 parts of piperazine and 32 parts of sulfur in 1000 parts of octanol. The pressure vessel is sealed, heated to 100 C. and kept at that temperature for 1 hour. It is then cooled to room temperature and vented. A precipitate is formed which is filtered and recrystallized from a 50 percent mixture of isooctane: and ethanol to yield hm- 1,4 piperazinediyl)bis(3,5-di-n-dodecyl-4-hydroxythiobenzaldehyde). I

In a reaction vessel equipped with a stirrer, heating means and temperature measuring means are placed 191 parts of 3-tert-butyl-4-hydroxy-S-ethylbenzaldehyde, 300 parts of piperazine and 160 parts of sulfur. The reaction mixture is heated to 135 C. and kept at that temperature for /2 hour. During this time a solid precipitates which is filtered and recrystallized from a 50 percent mixture of n-hexane and ethanol to yield a,a-(1,4-piperazinediyl) bis 3-tert-butyl-4-hyd roxyethylthiobenzald ehyde') Further, good results are also obtained in following the above procedure when reacting 3-methyl-5-tert-octyl- 4-hydroxybenzaldehyde with sulfur in a molar excess of piperazine to produce a,a' (1,4 piperazinediyl)bis(3- methyl-5-tert-octyl-4-hydroxythiobenzaldehyde).

Example 13 In a pressure-vessel equipped with venting means, heating means, a stirrer and temperature measuring means are placed 261 parts of 4-hydroxy-3,S-di-n-pentylbenzaldehyde, 77 parts of piperazine and 256 parts ofsulfur. The pressure vessel is sealed and heated to 300 C. for 5 minutes after which it is allowed to cool and then vented. The mixture is then triturated with n-hexane'. A solid precipitates which is filtered and recrystallized from a 50 percent mixture of n-hexane and ethanol to yield a,a'-( 1,4- piperazinediyl)bis(4 hydroxy 3,5 di-n-pentylthiobenzaldehyde).

Good results are also obtained when the above procedure is followed in reacting. 3-ethyl-4-hydroxy-5-isopropylbenzaldehyde with piperazine and sulfur to yield egos (1,4 piperazinediyl)bis(3 ethyl 4 hydroxy 5- isopropylthiobenzaldehyde) Example 14 In a reaction vessel equipped with heating means, a stirrer, temperature measuring means and a reflux condenser are placed 261 parts of 4-hydroxy-3-isopropyl-5- methylbenzaldehyde, 57 parts of piperazine and 320 parts of sulfur. The mixture is refluxed for 3 days. It is then cooled and triturated with n-hexane. A solid precipitates which is filtered and recrystallized from a 50 percent mixture of isooctane and ethanol to yield a,af-(1,4-piperazinediyl)bis(4 hydroxy 3 isopropyl 5 -'methylthiobenzaldehyde cent, and preferably from about 0.10 to about 2 percentof a compound of this invention.

The compounds of this invention find important utility as antioxidants in a wide variety of oxygen-sensitive material. Thus, liquid hydrocarbon fuels such as gasoline, kerosene and fuel oil are found to possess increased storage stability by the use of an antioxidant of this invention. Likewise, liquid hydrocarbon fuels such as gasoline which contain organometallic additives such as tetraethyllead, as well as other organometallic compounds which are used as fuel additives, attain appreciably increased oxidative stability by the practice of this invention. In addition, lubricating oils and functional fluids, both those derived from naturally occurring-hydrocarbons and those syntheetically prepared, are greatly enhanced by the practice of this invention. The addition of small quantities of the compounds of this invention to such materials as turbine, hydraulic, transformer and other highly refined industrial oils, waxes, soaps and greases, plastics, synthetic ploymers such aspolyethylene and polypropylene, organemetallic compositions such as tetraethyllead and tetraethyllead antiknock fluids, elastomers (including natural rubber), crankcase lubricating oils, lubricating greases, and the like, greatly increase their resistance to deterioration in the presence of air, oxygen or ozone.

The compounds of this invention are very useful in protecting petroleum waxparaffin wax and microcrystalline wax-against oxidative deterioration. They also find use in the stabilization of edible fats and oils of animal or vegetable origin which tend to become rancid especially during long periods of storage because of oxidative deterioration. Typical representatives of these edible fats and oils are linseed oil, cod liver oil, castor oil, soybean oil, rapeseed oil, coconut oil, olive oil, palm oil, corn oil, sesame oil, peanut oil, babassu oil, butter fat, lard, beef tallow, and the like.

The compounds of this invention are also very effective antioxidants for high molecular weight unsaturated hydrocarbon polymers, such as polybutadiene, methyl rubber, polybutene rubber, natural rubber, butyl rubber, GR-S rubber, GR-N rubber, piperylene rubber, dimethyl butadiene rubber and the like. Thus, one embodiment of the present invention is a rubber containing as an antioxidant therefor, a compound of this invention as defined above. Another part of this invention is the method of preserving rubber which comprises incorporating therein a compound of this invention as defined above. The stabilizer is incorporated into the rubber by milling, Banbury mixing, or similar process, or is emulsified and the emulsions added to the rubber latex before coagulation. In the various embodiments of this invention the stabilizer is used in small amounts, generally ranging from about 0.01 to about 5.0 percent, based on the rubber.

' The compounds of this invention are also useful in preventing oxidative deterioration in lubricating oil compositions. Thus, a prfeerred embodiment of this invention is a lubricating oil normally susceptible to oxidative deterio ration containing a small antioxidantquantity, up to 5 percent, of a compound of this invention as defined above.

To prepare the lubricants of this invention, an appropriate quantity-from about 0.001 to about 5 percent and preferably from about 0.25 to about 2 percent-of a compound of this invention is blended'with the base oil to be .crankcase oil was used.

.blending 1 percent by weight 9 protected. Suitable base oils include mineral oils and also synthetic diester oils, such as sebacates, adipates, etc. which find particular use as aircraft instrument oils, hy-

draulic and damping fluids and precision bearing lubriof this invention, recourse is had to the Polyveriform Oxidation Stability Test as described in the paper entitled Factors Causing Lubricating Oil Deterioration in Engines [-Ind. and Eng. Chem, Anal. Ed. 17, 302 (1945)]. 1 See also A Bearing Corrosion Test for'Lubricating Oils and Its Correlation with Engine Performance [Al.

Chem., 21, 737 (1949)]. This test effectively evaluates the performance of lubricating oil antioxidants. The test equipment procedure employed and correlations of the results with engine performance are discussed in the first paper cited above. this invention in oxygen-sensitive lubricating oil, efiective inhibition of oxidative deterioration is achieved.

- Comparatve tests wereconducted using the method and compared with the correspond- By employing'various compounds of apparatus essentially as described in thepublication first mentioned above. 'One minor modification was that the steel sleeve and copper test piece described in this publication were omitted from the apparatus.

In these tests Example 18 To 100,000 parts of a commercially available pentacrythritol ester having a viscosity at 100 F. of 22.4.

centistokes, and known in the trade as Hercoflex 600 is added 400 parts (0.4 percent) of a,a'-(1,4-piperazinediyl) bis(3 ter't butyl-5-mcthy1-4-hydroxythiobenzaldehyde) The resulting finished oil possesses markedly improved rcsistance against oxidative deterioration.

Example 19 To 100,000 parts of dioctyl sebacate having a viscosity of 210 F. of 36.7 SUS, a viscosity index of 159 and a molecular weight of 426.! is added 250 parts (0.25 percent) of a,a'-( 1,4-piperazinediyl) bis 3-(2-methylheptyl) 5-N-nonyl-4-hydroxythiobenzaldehyde) The compounds of this invention are also useful asadditives to functionalfluids and automatic transmission fluids. The primaryconstituent of a functional fluid is a refined mineral lubricating oil having carefully selected. minimum viscosity of 49 Saybolt Universal seconds SUS at 210 F. and a maximum viscosity of 7,000 SUS at 0 F generally a distillate oil, lighter than an SAE 10 motor oil. The oil usually amounts to between about 73.5 to

about 97.5 percent by weight of the finished fluid. Prefer- I ably, the base oil is selected from a paraffin base distillate such as a Pennsylvania crude.

' The fluids usually contain compounds which are char:

acterized by containing one or more organic components an initially additive-free 95 V1. solvent-refined SAE-lO The principal test conditions consisted of passing'50 liters of air per hour through the test oil for a total period of 20 hours whilemaintaining the oil at a temperature of 300 F. Oxidative deterioration of the oil was further promoted by employing as oxidation catalysts 0.05 percent by weight of'ferric oxide (as ferric 2-ethyl hexoate) and weight of the oil employed.

- Lubricating oils of this invention were prepared by of 'a,u.'( 1 ,4-piperazinediyl) bis(3,5-di-tert-butyl-4-hydroxythiobenzaldehyde) with the oil described above. These compositions were compared in the Polyveriform Test with a sample of the oil not containing the antioxidant. Whereas during the test the oil containing no antioxidant increased in acid number to;

12.3 and showed an increase in viscosity of 184 percent, the sample containing a,m'-(l,4-piperazinediyl)bis(3,5-ditert-butyl-4-hydroxythiobenzaldehyde) showed an acid.

number of only 3.6 and an increase in viscosity of only 40 percent thus showing a definite improvement over the base oil.

Example '15 To 1,000 parts of a solvent refined neutral oil (95 V.I.

and 200 SUS at 100 F.) containing 6 percent of a commercial methacrylate Type V.I.

approver which gives the finished formulation of a V.I. of 140 and a viscosity of 300 SUS at 100 F. is added 5 percent of a,a'-('l,4-piperazinediyl)bis(3,5di-tert-butyl 4 hydroxythiobenzalde- 'hyde).

Example 16 I To an additive-free solvent refined crankcase lubricating oil having a viscosity index of 95 and an SAE viscosity of 10 is added 0.001 percent of a, x'-.(1,4-piperazinediyl) bis( 3-hexyl-5-isopropyl-4-hydroxythiobenzaldehyde) Example 17 To 100,000 parts of a petroleum hydrocarbon oil.hav-. ing a gravity of 30.3 API at 60 F., a viscosity of 178.8 SUS at 100 F., a viscosity index of 154.2 and which contains 0.2 percent sulfur, is'added 200 parts of a,a'-(l,4- piperazinediyl)bis[3 (2 ethyldecyl)-5-N-dodecyl-4-hydroxythiobenzaldehyde)]. The, resulting oil possesses greatly enhanced resistance to oxidative deterioration.

0.10 percent by weight of lead bromide, both of these amounts being based upon the which maybe alkyl, aryl, alkaryl or aralkyl groups that are bonded to one or more metal-atoms through coupling groups such as sulfonate, hydroxyl, carboxyl and mercaptan. lithium, barium, strontium, and magnesium. The organic components contain oil solubilizing groups such as high molecular weight straight or branched chain.pa ratfins,'

aromatic or naphthenic rings, or contain a halogen. These metal compounds are present in the compounded fluid in a concentration 'rangeof between about 0.1 to about 5 percent by weight. These compounds include alkaline-'- earth metal salts of phenyl-substituted long chain fatty acids, alkaline-earth metal salts of capryl or octyl esters of salicylic acid, the alkaline-earth metal salts of petroleum sulfonic acids, the alkaline-earth metal salts of alkyl-substituted phenol sulfides, the salt of aluminum or the alkaline-earth metals with cetyl phenol, and the metal salts of wax-substituted phenol derivatives. Another class of additives are the so-called overbased phenates and sulfonat'es, which can be prepared by reaction between an alkyl phenol or alkyl phenol sulfide and an alkalineearth metal oxide or hydroxide at an elevated temperature. The overbased phenate formed from the reaction contains up to two or three times as much metal as the normal phenate.

. In addition, functional Typical components include anti-squawk additives, pour point depressants, foam inhibitors, rust preventatives, ex-

treme pressure agents, metal deactivators and viscosity index improvers.

, The following examples show typical functional fluids of this invention. The fluids are formed by mixing the ingredients togetherwhile heating the oil to a temperature up to 200 F.

Example 20 A fluid ofthis invention is prepared by blending parts of a dialkyl zinc dithiophosphate and 0.9 part of a The metal atoms may be aluminum, calcium,

fluids may contain additional 1 components which improve the properties of the fluid.-{

and a specific gravity dark, viscous liquid having a viscosity of 560 SUS at 210 F., a flash point of 420 F., a pour point of 30 F.

at 60/60 F. of 0.919.

Example 21 Another such fluid consists of 95 parts of a solventrefined, light acid-treated, clay-contacted, solvent dewaxed paraflin base distillate mineral oil (110 SUS at 100 F.), 0.1 part of a,a'-(1,4-piperazinediyl)bis[3,5-di-(ethyloctyl)-4-hydroxythiobenzaldehyde], 0.1 part of calcium octyl phenol sulfide, 2 parts of a sulfurized sperm oil having a sulfur content between -12 percent, a viscosity of 210 F. of 200 SUS and a pour point of 65 F., 0.3 part of an ester of an aromatic acid and wax-alkylated phenol having a molecular weightof approximately'450: 2.5

parts of a linear pale color isobutylene polymer of a controlled molecular weight having a viscosity of 3,000 SUS at 210 F., a specific gravity at (SO/60 F. of 0.875.-

Liquid hydrocarbon ,fuels employed in the operation of spark ignition combustion engines are also vastly improved in their storage stability by the practice of this invention. The following examples illustrate compositions of typical commercial gasolines which may be stabi1-' ized against oxidative deterioration by the inclusion therein of a compound ofthis invention.

Example 22 T0 1,000 parts of a gasoline containing 26.6 percent aromatics, 20.8 percent olefins, 52.6 percent saturates, and an API gravity of 62.1"is added 10 parts of a,a'-

(1,4 piperazinediyl)bis(3-isopropyl-5-methyl-4-hydroxythiobenzaldehyde) 1 Example 23'- To 10,000 parts of a gasoline containing 8.6 percent aromatics, 7.9 percent olefins, 83.5 percentsaturates and an API gravity of 68.5 is added 500 parts of a,ot'-(l,4- p'perazinediyl)bis(3 n-arnyl-S-tert-amyl-4-hydroxythiobenzaldehyde). 1 1 .v As noted in the preceding examples, the compounds of this invention are excellent antioxidants. This ability to prevent oxidation and deterioration of organic media. is completely unexpected since seemingly similar compounds show little or no such antioxidant activity.

While'the piperazine group of Formula I has been described without substituents-attached thereto, it is to be understood that this invention is not restricted to those compounds which are only unsubstituted on the piperazine but extends also to those compounds where the piperazine group hassubstituents such as alkyl, aryl, cycloalkyl, a'ralkyl, halogen and nitro groups.

wherein R and R are selected from the group consisting of alkyl groups containing from 1-20 carbon atoms and aralkyl groups containing from 7-20 carbon atoms.

2. The compound of claim 1 wherein. R is an alkyl group having from 1-l2 carbon atoms and R, is an alphabranched alkyl group having from 3-12 carbon atoms.

3. a, (1,4 piperazinediyl)bis(3,5 di q tert-butyl-4- hydroxythiobenzaldehyde) 4. The process of producing compounds of claim 1 which comprises'rcacting a piperazinediylbis-p-cresol having the formula:

I B1 H. H] I R] '/c-c\ H v 110- -N /N%- on g II, II] I wherein R, and R, are selected from the group consisting of alkyl groups containing from l-20 carbon atoms and aralkyl groups containing from 7-20 carbon atoms, with sulfur.- 1

5. Thefproess of producing-a compound of claim 1 which comprises reacting a benzaldehyde having the formula:

Hopes.)

wherein R and R, are selected from the group consisting of alkyl groups containing from 1-20 carbon atoms and References Cited by the Examiner UNITED STATES PATENTS 2,800,452 7/57 Bondi et al 252-515 2,805,998 9/57 Cantrell et al. 2S2-51.5 2,870,152 l/59 Schusteritz et al 260-268 2,927,924 3/60 Mills 260-268 2,997,474 8/61 Janssen 260-268 3,000,891 9/61 Janssen 260268 3,000,892 9/61 Janssen 260-268 'mvnio MARCUS, Primary Examiner.

WALTER A. MODANCE, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,186,993 June 1, 1965 Gordon G. Knapp It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, lines 58 and 59, strike out "with the present application"; column 3, lines 10 to 20, for the lower righthand portion of the equation reading OH read H Signed and sealed this 15th day of February 1966. L) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A COMPOUND HAVING THE FORMULA:
 4. THE PROCESS OF PRODUCING COMPOUNDS OF CLAIM 1 WHICH COMPRISES REACTING A PIPERAZINEDIYLBIS-P-CRESOL HAVING THE FORMULA:
 5. THE PROCESS OF PRODUCING A COMPOUND OF CLAIM 1 WHICH COMPRISES REACTING A BENZALDEHYDE HAVING THE FORMULA: 